It seems like other people have been having this same problem with other add ons when installing them from Creative Cloud:
The problem could be a network firewall blocking your Creative Cloud Desktop App from reaching Adobe's licensing servers or it could be a temporary problem with Adobe's licensing servers.
The easiest work around would be to login to https://timetracker.creativeworx.com/ and download the latest version of our extension directly from the Download Center which can be found in the Welcome menu in the top right corner.
If you're still experiencing problems please feel free to email us at firstname.lastname@example.org any time as David said and we could walk through more involved troubleshooting steps together to help us to understand the problem so we can write it up in our FAQs.
Thanks for your interest in and use of TimeTracker!